![](http://thenew.hp.com/img/s.gif) |
HP C++
HP C++ Class Library Reference Manual
Chapter 8 Stopwatch Package
The Stopwatch package provides ways to measure intervals of program
execution time. The package consists of a single class,
Stopwatch
. Typically, you use this class during the performance-tuning phase of
program development.
Stopwatch class
Provides the means to measure intervals of time between specified
program events.
Header
#include <stopwatch.hxx>
Alternative Header
#include <Stopwatch.h>
Declaration
class Stopwatch
{
public:
Stopwatch();
void start();
void stop();
void reset();
int status() const;
double system() const;
double user() const;
double real() const;
static double resolution();
};
|
Description
Objects of this class measure program execution time and return the
result in floating-point seconds. The class includes the
start
,
stop
, and
reset
functions familiar to users of a mechanical stopwatch.
You can time the entire program or select certain portions of the
program to time; for example, a specified loop or program module. You
can create a different
Stopwatch
object for each independent program activity, and name each according
to the activity you intend to measure.
Constructor
Stopwatch()
Constructs a
Stopwatch
object with both time and running status initialized to 0.
Member Functions
double real() const
Returns real time (clock time) in double-precision, floating-point
seconds. You can call this function while the stopwatch is running.
void reset()
Resets the current time measurement to 0 without affecting the value of
status()
. If
status()
is initially nonzero, time measurement continues uninterrupted after
resetting.
double resolution()
Returns the (system dependent) resolution of measured time in
double-precision, floating-point seconds.
void start()
Begins measuring program execution time when
status()
is initially 0 (
status()
becomes nonzero as a consequence of the call). If
status()
is initially nonzero, the call has no effect.
int status() const
Indicates whether the stopwatch is running (returns a value of 1) or
not running (returns a value of 0).
void stop()
Halts measurement of program execution time when
status()
is initially nonzero (
status()
becomes 0 as a consequence of the call). If
status()
is initially 0, the call has no effect.
double system() const
Returns the system CPU time in double-precision, floating-point
seconds. You can call this function while the stopwatch is running.
double user() const
Returns the user CPU time in double-precision, floating-point seconds.
You can call this function while the stopwatch is running.
System Environment
A typical value for the resolution of execution time is 1/60 second.
Example
|
Stopwatch w ;
w.start() ;
//...
// some computation you want to time goes here
//...
w.stop() ;
cout << "elapsed time was " << w.user() << "\n";
|
Displays the number of seconds the computation takes to run. The result
is a double-precision value.
|